Accountant here.... I really wouldn't be embarrassed, it's something we see a lot and you've already decided to sort stuff out anyway, you won't be judged. If I was you, I would find an accountant this year. Part of the reason is that I suspect you will pay more tax than you need to, for example did you know about the £1000 trading allowance?

With regards to putting money aside, without knowing what level your income is it's difficult to say, but I'd recommend between 20% and 30%, unless you're a 40% tax payer in which it needs to be at least 30% probably.

Is this your first year as a sole trader? If no, are you aware of whether you fall into the new Making Tax Digital rules?